Method of manufacturing clean-room compatible honeycomb tables

ABSTRACT

In order to render honeycomb tables with apertured table leaves clean-room compatible, sealing sheets are provided with projections corresponding in number and location to apertures in the table leaves and projecting into cells of honeycomb cores for a distance being several times smaller than the depth of such cores. These sealing sheets and their projections seal the honeycomb cells against the table leaf apertures inside the table leaves. Debris and lubricant residues accumulate inside these projections during provision of the table leaf apertures and are removed through these apertures preparatory to use of each honeycomb table in a clean room. The apertures are structured for receiving fasteners for attaching objects to the honeycomb tables. A load-bearing sealing structure may be molded from a sealing sheet or may otherwise be provided with cavities situated like the above mentioned projections. Sitting on top of the honeycomb core, that sealing structure bears the table leaf and objects or other loads placed or imposed on the table, in addition to ensuring clean-room compatibility.

BACKGROUND OF THE INVENTION Cross-Reference to Related Applications

This is a continuation-in-part of patent application Ser. No. 6/890,632,filed July 30, 1986 by Dennis C. Terry et al, now abandoned, as acontinuation-in-part of patent application Ser. No. 06/663,343, filedOct. 22, 1984 by Dennis C. Terry et al, assigned to the common assignee,herewith incorporated by reference herein, and issued as U.S. Pat. No.4,621,006, on Nov. 4, 1986.

FIELD OF THE INVENTION

The subject invention relates to honeycomb panels and tables, honeycombpanel and table manufacture, and optical tables including honeycomb andsimilar structures.

INFORMATION DISCLOSURE STATEMENT

This information disclosure statement is made pursuant to the duty ofdisclosure imposed by law and formulated in 37 CFR 1.56(a). Norepresentation is hereby made that information thus disclosed in factconstitutes prior art, inasmuch as 37 CFR 1.56(a) relies on amateriality concept which depends on uncertain and inevitably subjectiveelements of substantial likelihood and reasonableness, and inasmuch as agrowing attitude appears to require citation of material which mightlead to a discovery of pertinent material though not necessarily beingof itself pertinent. Also, the following comments contain conclusionsand observations which have only been drawn or become apparent afterconception of the subject invention or which contrast the subjectinvention or its merits against the background of developmentssubsequent in time or priority.

Utility and advantages of honeycomb structures, panels and tables invarious fields of technology are well known, as may, for instance, beseen from U.S. Pat. Nos. 3,784,146 by J. W. Matthews, issued Jan. 8,1974 for a horizontal vibration isolation system, 4,360,184 by W. J.Reid, III, issued Nov. 23, 1982 for a pneumatic device for attenuationof vertical, horizontal and rotational dynamic forces, 3,606,460, by M.J. Shannon, issued Sept. 20, 1971 and disclosing furniture and tableconstruction with honeycomb panels, 3,754,812, by H. Mohn, issued Aug.28, 1973 and disclosing optical elements with honeycomb support plate,3,765,993, by S. L. Raffensparger et al, issued Oct. 16, 1973 anddisclosing a layup machine for assembling honeycomb core panels,4,035,061, issued July 12, 1977 and 4,182,553, issued Jan. 8, 1980, byN. K. Sheridon, disclosing honeycomb display devices, and 4,066,249, byJ. G. Huber, issued Jan. 3, 1978 and disclosing a modular vacuum workarea with honeycomb core; all being herewith incorporated by referenceherein.

Reference may also be had to U.S. Pat. Nos. 3,070,480, by R. C. Breiner,issued Dec. 25, 1962, and 3,104,194, by A. T. Zahorski, issued Sept. 17,1963, both of which show honeycomb panels having corrugated sheetsinterposed between the honeycomb cores and outer panel sheets, and U.S.Pat. Nos. 3,087,565 and 3,087,571, by E. M. Kerwin, Jr., issued Apr. 30,1963 for apparatus for damping flexural movements.

Reference may also be had to brochures entitled Mechanical Properties ofHexcel Honeycomb Materials, TSB 120, and The Basics on Bonded SandwichConstruction, TSB 124, by Hexcel Corporation (1982 Revision).

For an extensive tutorial discussion on optical honeycomb tables,reference may be had to the 1983-1984 Catalog by the subject assignee,Newport Corporation, pp. 3 et seq., 2nd Edition, including discussion ofthe multilevel panel systems on pages 40 and 41 thereof.

In this respect, by way of example and not by way of limitation, amongthe most sensitive applications to which optical tables are put arethose involving interferometry, where tolerable relative displacementsof reflective elements are measured in fractions of a micron andallowable table top bending or twisting is typically much less than asecond of arc.

Even when requirements are less demanding, it is best to choose a tablesystem that offers that kind of performance, thereby eliminating anylikelyhood of table related problems.

The rigidity of a panel or table used in optical research is one of theprimary performance features and, for a given panel thickness and skin,depends largely on the shear modulus of the core.

For these and related reasons, honeycomb cores are greatly preferred forvery stable panel and table systems.

In the past, granite plates and slabs were frequently used in laserholography and interferometry work. However, while granite offers greatstability, the lack of a generally acceptable means of securingcomponents to granite surfaces, as well as the great weight of graniteslabs, is increasingly displacing them from laboratories and similarenvironments.

A major advantage of honeycomb panels or tables is that their top skinor table leaf can be provided with a large number of mounting holeswhich have a very minor effect on panel or table rigidity and strength.Typically, such mounting holes are present in great number and aretapped, thereby permitting the mounting of optical instruments and othercomponents in a wide variety of desired locations.

In some applications, the drilling and tapping of holes in the panel ortable top skin leaves residues in the cells of the honeycomb core. Wherethe honeycomb cores have to be very thick between top and bottom skinsfor high rigidity and stability, contaminants in the honeycomb cells aresometimes difficult to remove.

Reference may in this respect be had to U.S. Pat. No. 3,137,604, by L.R. Bosch, issued June 16, 1964 for a honeycomb structure and process ofmanufacture, but failing to suggest any solution to the latter problem.

The same applies to the proposal according to U.S. Pat. No. 4,370,372,by W. E. Higgins et al, issued Jan. 25, 1983 for a method of joininghoneycomb panels using a fastener element, and to the proposal accordingto U.S. Pat. No. 3,249,659, by W. D. Voelker, issued May 3, 1966 for amethod of making laminated panel structures in which perforations areprovided in reinforcing members between internal cells.

Efforts of providing honeycomb panels in non-analogous areas have workedagainst, rather than for, a solution, as may be seen from U.S. Pat. No.2,870,857, by E. E. Goldstein, issued Jan. 27, 1959 for a translucentacoustical correction ceiling construction, U.S. Pat. No. 4,294,329, byP. M. Rose et al, issued Oct. 13, 1981 for a double layer attenuationpanel, U.S. Pat. No. 4,300,978, by C. E. Whitemore et al, issued Nov.17, 1981 for a bonding tool for venting honeycomb noise attenuationstructures, and U.S. Pat. No. 4,465,725, by F. J. Riel, issued Aug. 14,1984 for another noise suppression panel.

These proposals teach preservation of internal flow-through capabilitybetween internal honeycomb cells in addition to flow-through to thepanel environment, which is just the opposite of what would be neededfor clean-room compatibility after contamination of cells duringmanufacture of the panels.

This, then, can cause problems in clean-room, vacuum and otherenvironments where contaminants are able to leave honeycomb cellsthrough apertures in the top skin to an extent producing a noticeableeffect in the particular environment.

In this respect, it has been claimed that the use of threaded inserts inlieu of tapped top skin holes avoids the use of oil that could affectdelicate optical opponents. Reference may in this respect be had to thebrochure entitled Optical Hardware, by Melles Griot (1983), pp. 2 to 6.Among the problems of that approach is, of course, the fact that even amedium sized table of, say, four feet by six feet size, requires overthree thousand threaded inserts which have to be individually positionedand attached to the top skin, if mounting holes one inch apart are to beprovided in the table top.

Another approach would be to close each tapped mounting hole with athreaded stud, before the honeycomb panel or table is put into service.This, too, would require the use and insertion of thousands of studs inpractical applications and, moreover, would, of course, only seal off,but not remove, oil and other drilling and tapping residues fromhoneycomb cells.

According to advertisements by Technical Manufacturing Corp., ofPeabody, Mass. 01960, which have appeared in Photonics, October 1985 andJanuary 1986, and in Lasers & Applications, September 1985, the tappedholes in the vibration isolation table leaf are individually equippedwith metal cups projecting into the honeycomb table cells. In the wordsof the advertisers, every threaded hole in the top surface is enclosedfrom below with a welded and epoxy-sealed metal cup, and no inserts areused. That is believed to be a rather cumbersome and expensiveprocedure. Also, those cups do not appear to impart a beneficialstructural or dynamic effect to the vibration isolation performance ofthe table.

This is confirmed in U.S. Pat. No. 4,645,171, by Ulf B. Heide, issuedFeb. 24, 1987 to Technical Manufacturing Corporation, and beingexpressly limited to non load bearing enclosures. References cited inthat patent include U.S. Pat. Nos. 3,176,662, by R. E. Williams, issuedApr. 6, 1965 for an illustrator's pen holder desk set and componentstherefor, 3,456,806, by S. M. Borston, issued July 22, 1969, for a haircurler stand, 3,601,343, by A. H. Sivaslian, issued Aug. 24, 1971, for astrain-free mount having beamlike support elements, 3,836,416, by R. L.Ropiequet, issued Sept. 17, 1974, for non-woven thermoplastic fabricsincluding filaments extruded through orifices in the die of an extrusionchamber, 4,221,014, by S. L. Davidson, issued Sept. 9, 1980, for a poststorage rack having openings in a support plate for drainage and foraccommodation of projecting post ends, 4,241,892, by I. B. Morris,issued Dec. 30, 1980, for an appliance skidboard having top and bottomperforations, and Federal Republic of Germany Pat. No. 836 401, byWilhelm Dichmann II, issued Apr. 10, 1952, for method and table forretaining papers, cardboard, plywood, metal foil, and the like, havingan apertured table top on a vacuum chamber.

None of these references suggest a solution for the problem at hand.

On the other hand, the common assignee hereof, as shown in the abovementioned parent U.S. Pat. No. 4,621,006, has provided clean-roomcompatible table systems which are relatively easy to manufacture, butare very effective in practice.

Reference may in this respect be had to the above mentioned SecondEdition of the Newport Corporation 1983-1984 Catalog, including p.32,second paragraph, and generally to The Newport Catalog No. 100,published 1987, and particularly to section A thereof, onVibration-Isolated Table Systems.

SUMMARY OF THE INVENTION

It is a general object of this invention to overcome disadvantages ormeet needs expressed or implicit in the Information Disclosure Statementor in other parts hereof.

It is a related object of this invention to provide improved honeycombpanels and tables, hereinafter simply referred to as "honeycomb tables."

It is a germane object of this invention to provide new or improvedmethods of manufacturing honeycomb tables.

It is also an object of this invention to render honeycomb tablesclean-room compatible.

It is a related object of this invention to improve the ease ofmanufacture of clean-room compatible honeycomb tables.

It is also an object of this invention to improve mechanical performanceof honeycomb tables while providing clean-room compatibility.

Other objects of this invention will become apparent in the furthercourse of this disclosure.

From one aspect thereof, the subject invention resides in a method ofmanufacturing a honeycomb table including a table leaf having an outsidesurface and apertures for receiving fasteners for attaching objects atthat outside surface and including a honeycomb core supporting thattable leaf and extending inside that table leaf between that table leafand a facing sheet spaced from that table leaf and having internalcells. The invention according to this aspect resides, morespecifically, in the improvement comprising in combination the steps ofproviding a sealing sheet with projections corresponding in number andlocation at least to the above mentioned apertures for projection fromthe table leaf for a distance being smaller than a spacing between theabove mentioned facing sheet and the table leaf, and providing thesealing sheet between the table leaf and the honeycomb core for sealingthe internal cells of the honeycomb core relative to the apertures inthe table leaf; with the projections of the sealing sheet projectingaway from the table leaf and the apertures in said table leafcommunicating with insides of the projections to render the honeycombtable clean-room compatible by enabling cleaning of the projections ofthe sealing sheet inside the table leaf through its apertures fromoutside of that table leaf.

From a related aspect thereof, the subject invention provides aload-bearing sealing structure with cavities corresponding in number andlocation at least to the table apertures and with a height smaller thana spacing between the facing sheet and the table leaf. The inventioninterposes that sealing structure between the table leaf and thehoneycomb core so that such sealing structure bears the table leaf andloads imposed on said table leaf and so that this sealing structureseals the internal cells of the above mentioned honeycomb core relativeto the above mentioned apertures in the table leaf. Apertures in thetable leaf are caused to communicate with cavities in the sealingstructure to render the honeycomb table clean-room compatible byenabling cleaning of these cavities inside the table leaf through theapertures from outside the table leaf.

From a related aspect thereof, the subject invention also resides in ahoneycomb table, comprising in combination, a table leaf having anoutside surface and apertures for receiving fasteners for attachingobjects at that outside surface, means for rendering the honeycomb tableclean-room compatible, including a sealing sheet having projectionscorresponding in number and location at least to the above mentionedapertures and extending from an inside of the table leaf for a firstdistance, a facing sheet spaced from the table leaf, and a honeycombcore supporting the sealing sheet and the table leaf and extendingbetween that sealing sheet and the above mentioned facing sheet for asecond distance being larger than the first distance and having internalcells between the sealing sheet and the facing sheet sealed off againstthe apertures by the sealing sheet.

From a related further aspect thereof, the subject invention alsoresides in a honeycomb table, comprising, in combination, a table leafhaving an outside surface and apertures for receiving fasteners forattaching objects at that outside surface, means for rendering thehoneycomb table clean-room compatible, including a sealing sheet havingprojections corresponding in number and location at least to theapertures and extending from an inside of the table leaf, a facing sheetspaced from the table leaf, and a honeycomb core supporting the sealingsheet and having first elements between bottoms of the projections andthe facing sheet, and second elements interconnected with the firstelements and extending along the first elements and in between theprojections.

Other aspects of the invention will become apparent from thisdisclosure, and no restriction to any aspect or invention is intended bythis Summary of the Invention.

No restriction to any particular sequence is intended by any recital ofsteps in any method claim or in any description of any method herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject invention and its various aspects and objects will becomemore readily apparent from the following detailed description ofpreferred embodiments thereof, illustrated by way of example in theaccompanying drawings, in which like reference numerals designate likeor equivalent parts and in which:

FIG. 1 top view of a honeycomb table, having parts broken away todisclose internal structure according to an embodiment of the subjectinvention;

FIG. 2 is an elevation of part of a honeycomb table during a phase ofits manufacture according to an embodiment of the subject invention;

FIG. 3 is a side view of the honeycomb table part of FIG. 2 on asomewhat enlarged scale and illustrates a further phase of themanufacture of the honeycomb table according to an embodiment of thesubject invention;

FIG. 4 is a view similar to FIG. 3, illustrating yet another phase inthe manufacture of the honeycomb table according to the latterembodiment of the subject invention;

FIG. 5 is a perspective view of a sealing sheet made according to anembodiment of the subject invention;

FIG. 6 is a detail view, on an enlarged scale, of part of the honeycombtable shown in FIGS. 1 to 4;

FIG. 7 is a section, with parts broken away, and taken on the line 7--7in FIG. 8, of a honeycomb table according to a further embodiment of theinvention;

FIG. 8 is a section taken on the line 8--8 in FIG. 7;

FIG. 9 is a view similar to FIG. 1, having parts broken away to show aload-bearing sealing structure according to a further embodiment of theinvention;

FIG. 10 is a view taken on the line 10--10 in FIG. 9;

FIG. 11 is a view taken on the line 11--11 in FIG. 10;

FIG. 12 is a view similar to FIG. 10 showing another embodiment of theinvention;

FIG. 13 is a view taken on the line 13--13 in FIG. 12; and

FIG. 14 is a view similar to FIGS. 1 and 9 showing yet anotherembodiment of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

The honeycomb table 10 whose top view is shown in FIG. 1 has a top skinor leaf 12, herein for brevity referred to as "table leaf." The subjectinvention has utility in the manufacture of various honeycombbreadboards, panels, tables and similar structures, herein for brevityreferred to as "honeycomb tables."

In practice, honeycomb tables of the type herein disclosed arefrequently used with other components and structures, such as in or withvibration isolation systems, as may be seen from the above mentionedNewport Corporation 1983-84 Catalog and from U.S. Pat. No. 3,784,146, byJohn W. Matthews, Ph.D., issued Jan. 8, 1974 and herewith incorporatedby reference herein.

The table leaf 12 is apertured, having a multitude of threaded or tappedmounting holes 13 therethrough, for an attachment of various optical andother components used on the honeycomb table for experimentation,research and development, or for industrial analysis, design and testingor a great variety of other purposes. While only a limited number ofapertures 13 are shown in FIG. 1, an actual honeycomb table for opticalpurposes typically has thousands of tapped mounting holes arranged in aregular grid pattern in parallel to the length and the width of thetable.

The honeycomb table 10 has a honeycomb core 14 extending between andsupporting the apertured table leaf 12 and a bottom or facing sheet 16spaced from the table leaf 12 by a first distance 17. The honeycomb core14 has internal cells 18 extending between the table leaf 12 and thefacing sheet 16. In the context of the subject invention, this does notmean that the honeycomb cells 18 extend onto the table leaf 12 tocommunicate with apertures 13 in the table leaf. Rather, the honeycombcells are sealed off, as more fully set-forth in the further course ofthis disclosure.

In the manufacturing method and construction shown in FIGS. 1 to 4, theillustrated preferred embodiment of the subject invention renders thehoneycomb table 10 clean-room compatible by sealing the cells 18 with asealing sheet 20 having projections 21 projecting from the table leaf 12by a second distance 22 several times smaller than the first distance17.

The honeycomb core 14 may be manufactured in a conventional manner. Byway of example, the above mentioned brochure TSB 120 describes andillustrates on pages 2 thereof the well-known expansion process ofhoneycomb manufacture, as well as the equally well-known corrugationprocess. In this respect, the expression "honeycomb" as herein employedand as generally used in industry is not restricted to exact hexagonalconfigurations. Rather, that expression is generally also applied tocore configuration composed of corrugated sheets that form cells ofother than hexagonal cross-section.

Of course, those skilled in the art will select the best cell or coreconfiguration for a given application. For instance, if highestprecision is essential, cheap substitutes are to be avoided, as theabove mentioned Newport Corporation 1983-84 Catalog points out on page 4thereof under the subtitle "Pseudo Honeycomb Panels." Nevertheless,corrugated sheets glued together at their crests may be suitable inhigh-performance honeycomb cores. This is illustrated in FIG. 14 by wayof example, where a honeycomb core 114 is shown as composed oflongitudinal ribs or panels 115 and corrugated sheets or panels 116interdigitated therewith and mounted thereon to provide the internal orhoneycomb cells 18 sealed off pursuant to the subject invention.

Various materials used in the manufacture of honeycomb structures mayalso be employed in the practice of the subject invention. For instance,the honeycomb core 14 may be made from an aluminum alloy, from steel orof plastic material, to name a few examples.

The illustrated preferred embodiment of the invention resides in amethod of manufacturing a honeycomb table 10 including a table leaf 12having an outside surface and apertures 13 for receiving fasteners 48for attaching objects 44 at that outside surface 41 and including ahoneycomb core 14 supporting the table leaf and extending inside thattable leaf between that table leaf 12 and a facing sheet spaced 16 fromthe table leaf and having internal cells coinciding spatially with theapertures 13. Not all of the cells 18 need to coincide with an aperture.Some of the honeycomb cells may be located between apertures 13.

However, the sealing sheet 20 is provided with projections 21corresponding in number and location to the apertures 13 for projectionfrom the table leaf 12 for a distance 22 being several times smallerthan a spacing 17 between the facing sheet 16 and the table leaf 12. Inparticular, the sealing sheet 20 is provided between the table leaf 12and the honeycomb core 14 with the projections 21 projecting away fromthe table leaf 12 into the cells 18.

The apertures 13 may then be provided in the table leaf 12 ascommunicating with insides of the projections 21. The honeycomb tablemay thereafter be rendered clean-room compatible by cleaning theprojections 21 inside the table leaf through the apertures 13 fromoutside of that table leaf 13.

For attachment of the sealing sheet 20 to the table leaf 12 and of thehoneycomb structure 14 to the sealing sheet, or vice versa, during anysuitable and desired phase of the table assembly, reference may be hadto FIG. 6, in addition to FIG. 2, for instance.

The sealing sheet 20 and the table leaf 12 are attached to each otherwith an adhesive 31 applied to that sealing sheet and to an insidesurface 51 of the table leaf, opposite the outside 41. The sealing sheet20 and the honeycomb core 14 are attached to each other with an adhesive32 applied to that sealing sheet 20 and to the honeycomb core 14.

The above mentioned brochures TSB 120 and 124 contain tutorial commentson adhesives preferred for such purposes.

The sealing sheet 20 and the honeycomb core 14 are attached to eachother at portions 23 of the sealing sheet 20 between its projections 21.Similarly, the sealing sheet and the table leaf 12 are attached to eachother at the portions 23 of the sealing sheet between its projections21.

The sealing sheet 20 preferably is used as an intermediary in anattachment of the honeycomb core 14 to the table leaf 12.

According to the illustrated preferred embodiment of the invention, theprojections 21 are sealed except for communication through the apertures13. By way of example, the projections 21 are provided with closed sides25 and closed bottoms 26 relative to the honeycomb core 14 or internalcells 18.

As diagrammatically indicated in FIG. 5, the sealing sheet 20 may bemade by providing a sheet of sealing material 28 and providing thesealing sheet with the projections 21 by drawing these projections insaid sheet of sealing material 28, as symbolically indicated by arrow29. Stamping or preferably vacuum forming may be used for this purpose.

Various materials, including metal, such as steel and aluminum, andformable plastics, may be used for making and forming the sheet 20, aslong as the resulting sheet structure 20, 21 is sufficiently tight toprevent contamination of the honeycomb cells 18 during the provision ofthe apertures 13 and to preclude any contaminant that may be in thecells 18 from escaping through the apertures 13 when the table 10 islocated in a clean room.

Within the scope of the subject invention, the projections 21 and cells18 may have like or similar cross-sectional configurations. However,according to a preferred embodiment of the invention, the internal cells18 have a first cross-sectional configuration, and the projections 21project into these internal cells, but have a second cross-sectionalconfiguration different from that first configuration. This permits thehoneycomb core 14 to be structured for its best performance, whilepermitting optimum structuring of the sealing sheet 20 and projections21 for their best mechanical and dynamic performance in the context ofthe honeycomb table system. In this respect, the structuring of thesheet and projection system 20, 21 may combine with the structuring ofthe table leaf and honeycomb system 12, 14, 16 for optimum overallperformance in the use of the resulting table system in research,development, testing and other functions.

Accordingly, where the internal cells 18 have a hexagonal configuration,the projections 21 which project into these internal cells preferablyhave a cross-sectional configuration different from a hexagonalconfiguration.

By way of example, the projections 21 may be provided with a rectangularconfiguration. On the other hand, the side view of the solidlyillustrated projection 21 in FIG. 2 and the side view of the solidlyillustrated projection 21 in FIG. 3 may be taken as an illustration of atruncated cone or of the fusto-conical configuration mentioned in thenext paragraph hereof. In either case, FIGS. 2 and 3 show that theprojections 21 or the cavities 45 may be provided with a gradualdiminution of diameter or taper away from the table leaf inside.

According to the illustrated preferred embodiment, the projections 21are truncately pyramidal; that is, in the form of truncated pyramids.Other options include fusto-conical configurations. In either case, theflat tops 26 of the projections 21 are in a plane spaced from the insidesurface 51 of the table leaf 12 by the short distance 22.

The honeycomb core 14 supporting the sealing sheet 20 and the table leaf12 extends between that sealing sheet and the facing sheet 16 for adistance 17 being several times larger than the latter distance 22 andhas its internal cells 18 between the sealing sheet and the facing sheetsealed off against the apertures 13 by that sealing sheet 20, includingits projections 21, which project into the internal cells 18 and whichare sealed except for communication through the apertures 13 in thetable top.

The table leaf 12 is preferably pulled flat on the vacuum table 33 afterthe sealing sheet 20 has been attached to that table leaf 12. Thehoneycomb core 14 may then be bonded to the sealing sheet 20 or toportions 23 thereof. As shown in FIG. 2, a flat plate 34 resting on thefacing sheet 16 and applying a bonding force in the direction of arrows35, may be employed in conjunction with the vacuum table 33 in bondingthe honeycomb section 14 with attached facing sheet 16 to the sealingsheet 20 at portions 23.

That sealing sheet 20 may thus be employed as an intermediary forbonding the table leaf 12 and the honeycomb sections 14 to each other.According to the embodiment shown in FIG. 2, the table leaf 14, sheet 20and honeycomb section 14 are bonded together before the apertures 13 aredrilled into the table leaf 12.

Once the cells 18 of the honeycomb structure have been sealed off by thesealing sheet 20, the apertures 13 may be provided in the embodiment ofFIGS. 2 and 3. As shown in FIG. 3, the honeycomb structure 14 withattached sealing sheet 20, table leaf 12 and facing sheet 16 may beinverted relative to the position shown in FIG. 2 and may be placed on aworktable 36. A machine tool 37 may then be employed to first drill andthen tap the apertures 13, row by row across and along the table leaf12.

In practice, a series of drills, followed by a series of tapping bits isemployed to this end. For the purpose of illustration, FIG. 3 showsdrills 38 on the left-hand side and tapping bits 39 on the right-handside thereof.

As indicated at 43 in FIG. 3, drilling and tapping of the apertures 13leaves a certain residue in the honeycomb cells. By way of example, thatresidue may be composed of a cutting oil or other medium used in themaking of the tapped apertures, as well as particles of the metal orother material from which the table leaf 12 is made.

Within the scope of the subject invention, the drilling, tapping andcleaning steps shown in FIGS. 3 and 4 may be carried out before thesealing sheet 20 with attached apertured table leaf 12 is bonded to thehoneycomb section or core 14. In that respect, no limitation to acertain sequence of steps is intended by listing certain steps insequence in any method claim hereof. Rather, within the intended scopeof the claimed methods, apertures 13 can be provided in the table leafbefore or after the honeycomb section 14 is attached to the sealingsheet 20.

In either case the honeycomb table 10 is rendered clean-room proof bycleaning the projection insides 45 through apertures 13 in the aperturedtable leaf prior to use of the table in a clean room or even prior tobonding of the honeycomb core section 14 to the sealing sheet 20 and thetable leaf 12 combination. Forced flushing, such as with a cleaningliquid, may be employed.

It may be noted that the sealing sheet 20 provides the insides orcavities in its projections 21 and that like or similar cavities 45 areprovided in or by the other load-bearing sealing structure of FIGS. 9 to14.

If the cells of the honeycomb structure 14, extending all the way fromthe bottom sheet 16, communicated with the apertures 13, then it wouldbe practically impossible with thick table structures to remove allpossible contaminants from such elongate cells 18. However, the sealedoff shallow spaces 45 in the small cup-like projections 21 are readilycleaned without great problems.

By way of example and as illustrated in FIG. 4, the table leaf 10 andsealing sheet 20 combination, with or without honeycomb core 14 andfacing sheet 16 section, is inverted and placed in the vacuum table 33,and the residues or contaminants 43 are readily removed from the shallowcups 21 or cavities 45 through the tapped apertures 13. For instance,the residues 45 may be pulled with the aid of a vacuum through channels47 of the vacuum table 33.

The table structure may be finished in a conventional manner by encasingit in an appropriate frame. Damping media may be added as desired. Thefinished table structure may once more be subjected to the cell cleaningprocess shown in FIG. 4 before it leaves the plant. If desired, theentire cell cleaning operation could be performed only after the table10 has otherwise been completely finished.

According to the best mode currently contemplated for carrying out thesubject invention, the sealing sheet 20 has base portions 23 attached tothe inside 51 of the table leaf 12 and has cups or projections 21integral with, and projecting from, these base portions. The integralcups 21 thus project away from the table leaf 12 at locations where thefastening apertures 13 are or are to be located. The cups 21 alsoproject into the cells 18 for sealing the internal cells against theapertures 13 inside the table leaf 12 or inside the honeycomb table 10for that matter.

As disclosed in or in connection with FIG. 2, the means for attachingthe sealing sheet sections 23 include an adhesive 31 on correspondingportions of the inside surface 51 of the table leaf 12.

The projection or cups 21 are shallow relative to the cells 18, butstill deep enough as not to interfere with the normal operation of thehoneycomb table. For instance, if fastening bolts 48 are threaded intothe apertures 13, then the otherwise shallow cups 21 preferably aresomewhat longer than these bolts, if their length exceeds the thicknessof the table leaf 12. Accordingly, even if the bolt exceeds suchthickness, the optical or other component 44 still can readily beattached to the table leaf 12, since the bolt will then be accommodatedwithin the sealing sheet projections 21. This will not have an adverseeffect at that point, since no contaminant is introduced into thehoneycomb cells thereby.

Also, it is much easier to clean the cavities 45 through the apertures13 at any time, than it would be if the depth of the internal cells 18would have to be cleaned, if that were possible in practice.

The honeycomb table 61 according to the preferred embodiment of theinvention shown in FIGS. 7 and 8 is similar in structure and method ofmanufacture as the honeycomb table shown in FIGS. 1 to 6.

In particular, the honeycomb table 61 has a honeycomb core 62 composedof interconnected first and second elements 63 and 64. The type ofhoneycomb structure shown in FIGS. 7 and 8 may also be employed in thehoneycomb table of FIGS. 1 to 4, and falls in its structural designationunder the broad definition of "honeycomb" set forth above or otherwisemodernly customary in the trade.

By way of example, the first honeycomb core element 63 may have awrinkle, pleated, zig-zag, sinusoidal or other corrugated structure.

The first honeycomb core elements 63 are provided between bottoms of theprojections 21 and the facing sheet 16. On the other hand, the secondhoneycomb core elements 64 are extended in between the projections 21 ofthe sealing sheet 20. In this manner, the second elements 64 areprovided from the facing sheet 16 to in between the projections 21.

Accordingly, while the projections 21 project into the honeycomb cells18 in the embodiment shown in FIGS. 1 to 4, the honeycomb or other cells66 of the core structure 62 are located below or beyond the projections21 in the embodiment shown in FIGS. 7 and 8.

In this respect, the honeycomb core 62 or any one or more of itselements may be interconnected with the sealing sheet 20 and/or with itsprojections 21. In practice, this improves the manufacturing process andrenders the resulting clean-room compatible honeycomb tablesstructurally and dynamically more effective for their vibrationisolation and other functions.

For instance, as shown in FIGS. 7 and 8, the first honeycomb coreelements 63 may be interconnected with the projections 21 at theirbottoms 26.

In the embodiment shown in FIGS. 7 and 8, the first core elements 63extend below the projections 21 back and forth between the secondelements 64. However, it should be understood that the principledisclosed with the aid of FIGS. 7 and 8 is applicable within the scopeof the subject invention to other kinds of honeycomb core structures.

End portions of the second elements 64 shown in FIGS. 7 and 8 areattached to the sealing sheet 20 in between the projections 21. Forinstance, such end portions of the honeycomb core elements 64 may beattached to the above mentioned portions 23 of the sealing sheet 20between the projections 21.

Alternatively, as shown at 67 in FIG. 7, portions of the second coreelements 64 may extend past the sealing sheet or sheets 20 to the tableleaf 12 itself, being, for instance, attached to an inside surface 51thereof.

As also indicated at 67 in FIGS. 7 and 8, the sealing sheet structuremay actually be composed of at least two sealing sheets 20 withprojections 21. In fact, several of the sealing sheets 20 shown in FIG.5 may be employed side by side at the inside surface 51 of largerhoneycomb tables 12, 61, etc.

In practice, the one or several sealing sheets 20, provided withprojections 21, may be provided or employed to reinforce the table leaf12. Frictional forces between structural members including the tableleaf 12, sealing sheet or sheets 20 and honeycomb core structure 62 maybe employed to provide damping and improved dynamic performance of thetable structure.

These and similar effects may be enhanced by providing damping masses 69on the sealing sheet 20 in between the projections 21. This refinementmay be applied to the embodiment of FIGS. 1 to 4, as well as to theembodiment of FIGS. 7 and 8, for instance. However, as more particularlyshown in FIG. 7, the damping masses 69 may be employed as adhesivesuniting the extended end portions of the second core elements 64 withthe sealing sheets 20 and its projections 21 and portions 23.

In fact, as shown at 67 in FIG. 7, the damping masses 69 may even beemployed for attaching projecting end portions of the second elements 64to portions of the table leaf 12. There are epoxy and other adhesivefillers that may be employed as damping masses 69. A showing of suchdamping masses 69 has been omitted from FIG. 8, so as to avoid anobstruction of details of that view.

In practice, each aperture 13 should be covered or sealed at the bottomthereof, by one of the projections 21. Of course, even if an occasionalaperture in the table leaf is not so sealed, the table would still besatisfactory in most if not practically all clean-room environments.However, it is greatly preferred that each aperture 13 in the table leafbe sealed off at the bottom thereof by a projection 21 projecting fromthe sealing sheet or sheets 20.

The projections 21 correspond in number and location at least to theapertures 13. In practice, there may, however, be more projections thanthere are apertures. In that case, only some of the projections, such asalternate projections 21, would seal off an aperture 13, while theremaining projections would simply extend from solid portions of thetable leaf 12 in between apertures 13. By way of example, furtherprojections 21 in addition to those needed for providing clean-roomcompatibility, may be employed if this is more advantageous in themanufacture of particular honeycomb tables or if this is necessary ordesirable to improve the structure and dynamic performance of certainvibration isolation tables.

In this respect, and in general, and as already pointed out on page 5 ofthe above mentioned 1983-84 Newport Corporation Catalog, 2nd Edition,the rigidity of a honeycomb table or panel is one of the primaryperformance features, and for a given panel thickness and skin, itdepends largely on the shear modulus of the core.

This can be seen by examining the expression for the deflection, δ, of ahoneycomb panel simply supported at its ends with a point load in thecenter: ##EQU1## wherein: P=Point load

L=Table length

E=Skin Young's Modulus

b=Table width

T=Skin thickness

H=Table thickness

G=Core shear modulus

The first term in this equation is the deflection due to bending and thesecond term is the deflection due to shear. In most cases, the skinmaterial and panel thickness were the dominant design features, and oncespecified, it sufficed to make the shear modulus of the core, G,sufficiently large that the shear term is small compared with thebending term. Examination of the bending term shows that this required amuch higher shear modulus, G, for panels that are very rigid inbending--i.e., panels that are thick compared to their length, such aswith Research Series table tops of the assignee of the entire interesthereof.

The subject invention, while solving the problem of clean-roomcompatibility, provides the researcher and honeycomb table designer witha tool to improve table structure and performance.

In this respect, the ratio δ/P derived from equation (1) may be viewedas indicating load-bearing capacity. As already mentioned above inaccordance with the subject invention, the structuring of the sheet andprojection system 20, 21 may be combined with the structuring of thetable leaf and honeycomb system 12, 14, 16 for optimum overallperformance in the use of the resulting table system in research,development, testing and other functions.

As already indicated above, the honeycomb core 62 or any one or more ofits elements may be interconnected with the sealing sheet 20 and/or withits projections 21 to improve the manufacturing process and render theresulting clean-room compatible honeycomb tables structurally anddynamically more effective for their vibration isolation and otherfunctions. One or several sealing sheets 20, provided with projections21, may be provided or employed to reinforce the table leaf 12.Frictional forces between structural members including the table leaf12, sealing sheet or sheets 20 and honeycomb core structure 62 may beemployed to provide damping and improved dynamic performance of thetable structure.

These and similar effects may be enhanced by providing damping masses 69on the sealing sheet 20 in between the projections 21.

From these considerations in general, and from equation (1) includingfactors E, T and G in particular, it may be seen that the sealing sheet20 with projections 21 in effect performs a load-bearing function. Load,in this respect, may be understood as signifying the factor P inequation (1) or the concept of load in physics, as applied to theillustrated table structures or to other structures within the scope ofthe subject invention.

Moreover, where the sealing sheet 20 is interposed between the tableleaf 12 and the honeycomb core 14, it performs a load-bearing functionin the truest sense of the word, bearing not only the table leaf 12 ontop of the core 14 and bottom skin 16, but bearing also the load ofobjects, such as the illustrated object 14 on top of that corestructure.

Even projections 21 themselves participate in a load-bearing function.By way of example and not by way of restriction, FIGS. 7 and 8 showprojections 21 resting on the above mentioned first honeycomb coreelements 63, thereby bearing, on top of those core elements, the load ofthe table leaf 12 including objects 44 positioned thereon.

FIGS. 9 et seq. show further embodiments according to the subjectinvention of load-bearing sealing structures.

In particular, FIGS. 9 to 11 show a load-bearing sealing structure 71having cavities 45, which, like the cavities 45 of the sealing sheet 20shown, for instance, in FIG. 4, correspond in number and location atleast to the apertures 13 and extend from an inside 51 of the table leaf12 for a first distance 72 which may be equal or similar to the distance22 shown in FIG. 4, and which is also several times smaller than theabove mentioned first distance 17, which is the spacing between thefacing sheet 16 and the table leaf 12.

The sealing structure has a height 74 several times smaller than thatspacing between the facing sheet and the table leaf, shown as the firstdistance 17. The overall height of the sealing structure 71 may beconsidered to include downward projections 76, with a height 75.However, since these elements 76 project into cells 18 of the honeycombstructure 14, the effective height of the sealing structure, on top ofthe honeycomb core 14, is actually the height shown at 74.

In particular, the invention interposes the sealing structure betweenthe table leaf 12 and the honeycomb core 14, so that such sealingstructure 71 bears the table leaf and loads 44 and 78 imposed on suchtable leaf.

According to the invention, the sealing structure 71 includes means,such as the walls 79 of the cavities 45, supported by the honeycomb core14, for bearing the table leaf 12 on top of that honeycomb core and forbearing loads imposed by objects 44 and 78 on the table leaf.

It may be recalled in this respect that the above mentioned Heide U.S.Pat. No. 4,645,171 teaches the use of non-load-bearing enclosures 24 forclean-room compatibility purposes. By sharp contrast thereto, thesealing structures 20 and 71 according to the subject invention, andeven the cavity enclosures 79, are load bearing as herein shown andtaught.

The sealing structure 71 and the table leaf 12 are attached to eachother, such as with an adhesive 31 applied to the sealing structure andto an inside surface 51 of the table leaf, opposite the outside 41thereof.

Similarly, the sealing structure and the honeycomb core are attached toeach other with an adhesive 32 applied to that sealing structure 71 andto the honeycomb core 14. In particular, the sealing structure and thehoneycomb core 14 may be attached to each other at portions of thatsealing structure 71 located at the cavities 45. The sealing structureand the table leaf 12 may be attached to each other at portions of thesealing structure between the cavities 45.

According to a preferred embodiment of the subject invention, thesealing structure 71 is used as an intermediary in an attachment of thehoneycomb core 14 to the table leaf 12. The cavities 45 are sealed,except for their communication through the table top apertures 13,through which they may be cleaned, if and when necessary for clean-roomcompatibility. The cavities 45 are provided with closed sides and closedbottoms relative to the honeycomb core 14 or its internal cells 18.

As an exception to that general principle of the subject invention, anembodiment thereof provides the sealing structure 71, at the bottom ofeach cavity 45 communicating with an aperture in the table leaf, with abreak-out 81 aligned with that aperture 12, to permit a fastener 82extending through that aperture 13 and that cavity 45 to break throughthe sealing structure 71 without damage to the sealing structure and thehoneycomb core.

In particular, FIG. 10 shows at 84 a break-out 81 broken out at leastpartially by a fastening bolt 82 which, below the table leaf 12, islonger than the depth of the cavity 45. Such a breakout 84 is anexception to the general sealing of the cavities 45 except forcommunication through the apertures 13, and the sealing of suchapertures and cavities relative to the cells 18 of the honeycombstructure 14. However, such an occasional breakout 84 is like a safetyfuse, in that it prevents long bolts 82 from separating the table leaf12 and sealing structure 71 from each other and from even damaging thecore 14. In other words, an occasional breakout, such as shown at 84 inFIG. 10, is tolerated in the interest of preserving the overallintegrity of the integral table leaf, sealing and core structures or, inother words, of the overall table structure 10.

According to a preferred embodiment of the invention, the sealingstructure 71 is provided with projections 76 extending into cells 18 ofthe honeycomb core 14. For one thing, these downward projections 76 aidin a relative alignment of the honeycomb core 14, internal cells 18,sealing structure 71, cavities 45, table leaf 12 and apertures 13 in themanufacture of the table structure 10.

Moreover, the projections 76 reinforce a periphery of the break-out 81with a hollow projection. Put differently, the projections 76 extendaround break-outs 81 in the sealing structure 71 aligned with apertures13 to permit a fastener 82 extending through such an aperture and thecorresponding cavity 45 to break through the sealing structure, as shownat 84 in FIG. 10, without damage to the sealing structure 71 andhoneycomb core 14, or without damage to the integrity of the tablestructure, for that matter.

Other than such occasional breakouts 84, the principle according to thesubject invention prevails, that the cavities 45 have closed sides 79and closed bottoms relative to the internal cells 18 of the honeycombcore.

As shown by the block 86 in FIG. 10, the sealing structure 71 may bemolded from a sheet of sealing material. For instance, a flat sealingsheet, similar to the sealing sheet 20 without projections 21, may beprovided and the sealing structure 71 and cavities 45 may be molded fromsuch a sheet of sealing material, such as by vacuum drawing. Othermethods of making the sealing structure 71 include an injection moldingthereof. The sealing structure 71 may, for example, consist of a moldedsheet of sealing material which has been given the desiredconfiguration.

The cavities 45 may be provided with a predetermined or desiredconfiguration. For instance, where the internal cells 18 have a firstcross-sectional configuration, the cavities 45 may be provided with asecond cross-sectional configuration different from that firstconfiguration. By way of illustrated preferred embodiment of theinvention, the cavities 45 are provided with a rectangularcross-section.

As seen particularly well in FIG. 9, sides or walls 79 of the cavities45 of the sealing structure 71 are arranged or extend in parallel tosides 88 and 89 of the table leaf 12. This is also the case with theembodiment shown in FIGS. 12 and 13, more fully described below.

However, reverting to the embodiment shown in FIGS. 9 to 11, the sealingstructure of that embodiment is provided with a top sheet 91 havingupper portions of the cavities 45 extending therethrough, and thesealing structure 71 is rendered flexible by providing a multitude ofslots 92 and 93 extending between the cavities 45 to the top sheet 91.Put differently, these slots extend from the top sheet 91 right throughthe bottom of the sealing structure 71.

Within the scope of the invention, only one set of slots need to beprovided. For instance, slots 92 may be provided in parallel to thetable side 98, as seen in FIG. 10. However, the preferred embodimentsaccording to FIGS. 11, 13 and 14 provide a pattern of crossed slots 92and 93 having the cavities 45 located therebetween or therein between.

In the case of the embodiment seen in FIG. 11, the crossed slots 92 and93 extend through the bottom region of the sealing structure 71. This isalso the case in the embodiment shown in FIG. 14, as seen from thedotted lines at 92 and 93 therein. However, that embodiment may be inthat respect more like the embodiment shown in FIGS. 12 and 13, ifrequired for a certain damping or other effect.

In particular, the embodiment shown in FIGS. 12 and 13 provides itssealing structure 94 with a bottom sheet 95 extending in this case inparallel to the table leaf 12, but at a distance thereto correspondingapproximately to the height 74 of that sealing structure, whichcorresponds to the sealing structure 71 shown in FIGS. 10 to 11.

The sealing structure 94 is rendered flexible by providing again amultitude of slots extending between the cavities 45 to the bottom sheet95. By way of example, there again may be a pattern of crossed slots 92and 93 having the cavities 45 located therebetween. However, this timethe crossed or other slots 92 and 93 extend to the bottom sheet 95. Putdifferently, it may be said that the slots 92 and 93 extend from thebottom sheet 95 of the sealing structure 94 directly to the table top orleaf 12 or to an adhesive or the like located at the underside 51thereof.

The remainder of the sealing structure 94 shown in FIGS. 12 and 13 maybe the same as the sealing structure 71 shown in FIGS. 9 to 11, andidentical or similar adhesives and other techniques may be employed forunifying the intermediary sealing structure 94 into a table structure 96together with the apertured table leaf 12, core 14 and bottom sheet 16.

The same essentially applies to the sealing structure 98 shown in FIG.14. The cavities 45 again may be provided with, or have, a rectangularcross-section. However, according to the embodiment shown in FIG. 14,the sides of the cavities 45 are arranged at angles to the sides 88 and89 of the table leaf 12. Put differently, diagonals 100 and 101 of therectangular cavities 45 are parallel to sides of the table leaf 88 and89, respectively.

As the embodiment shown in FIGS. 9 to 11, the embodiment shown in FIG.14 provides its sealing structure with a top sheet 91 through which thecavities 45 extend toward or to the table leaf 12. In that case, theslots 92 and 93 would extend through the bottom region of the sealingstructure 98.

However, within the scope of the invention, the diagonally extendingsealing structure 98 may be realized by providing that sealing structurewith a closed bottom sheet, as shown at 95 in FIGS. 12 and 13. In thatcase, the slots 92 and 93 would extend from that closed bottom rightthrough the top of the sealing structure 98, and to the table leaf 12,as do the slots 92 and 93 in the embodiment of FIGS. 12 and 13. Thesealing structure 98 may also be provided with projections 76 andcut-outs 81 and may in other respects be like the other embodiments,except as expressly noted to the contrary herein.

The subject invention, and even the illustrated embodiments thereof,provide the table designer, researcher, developer and manufacturer witha wide variety of sealing structures to choose from.

For one thing, it should be recalled at this point that the core 14 neednot necessarily have a hexagonal honeycomb configuration, but may be ofa wrinkle, pleated, zig-zag, sinusoidal or other corrugated structure,inasmuch as the expression "honeycomb" has acquired a secondary meaningin optical table construction and related areas, covering all kind ofstructures, in addition to the original honeycomb configuration.

Accordingly, depending on the actual structure and configuration of a"honeycomb" core, the table designer and the manufacturer may find itmore advantageous to employ a diagonally arranged sealing structure,such as the structure 98 shown in FIG. 14, rather than the rectilinearlyarranged sealing structures 71 and 94 of FIGS. 9 to 12. In addition oralternatively, the table developer or designer may prefer the diagonallyarranged sealing structure 98 for specific load-bearing properties, incombination with a given overall table structure or desired operation.

Of course, the converse could be true in a given situation, and itshould be remembered that the load-bearing properties of a sealingstructure in the subject context not only concern the ability to carrythe weight of the table leaf 12 and of whatever objects may be mountedthereon, but additionally or alternatively, concern the load-bearingimplications of equation (1) set forth above, and of its derivatives.

In this respect and in general, it may be noted that sealing structuresas herein disclosed may have more cells than there are mountingapertures 13 in the table leaf 12. For instance, FIG. 14 shows cells 103of the sealing structure 98 which doe not coincide with any of theapertures 13. Other cells of the sealing structure 98, that coincidewith mounting apertures 13 are provided with the above mentionedcavities 45. However, cells 103 that do not coincide with any mountingaperture, need not be provided with cavities. For instance, if thesealing structure has a top sheet 91 as in FIGS. 9 to 11 and 14, thecavities 45 need only extend through such top sheet where any mountinghole 13 in the table leaf 12 is located. At other portions of thesealing structure, the top sheet 91 may be solid, such as at thelocations 103, where no mounting hole 13 is located.

Similarly, where the sealing structure is provided with a bottom sheet95, no cavities need be provided at portions of the sealing structure 94where there is no corresponding aperture 13. By way of example, FIG. 12shows a solid element 105 for the sealing structure 94 where no mountingaperture 13 is located in the table leaf 12.

In the context of the sealing structures herein disclosed, solidelements interdigitated or otherwise mixed with cavity-containingelements may be beneficial to the load-bearing function in a broadsense, or to other perimeters of table manufacture and performance. Forthe same reason, it is within the scope of the subject invention toprovide cavities 45 in the sealing structures 20, 71, 94 and 98, evenwhere there are no coincident mounting apertures 13 in the table leaf.Again, this gives the researcher, developer, table designer andmanufacturer a variety of alternatives to choose from for best tableconfiguration and performance for all kind of purposes and applications.

As already disclosed in the Terry et al patent application Ser. No.06/663,343, filed Oct. 22, 1984, to which the subject patent applicationgoes back under 35 USC 120, and as shown in its resulting Terry et alU.S. Pat. No. 4,621,006, the drawings and other disclosure of which areherewith incorporated by reference herein, an aspect of the inventionresides in a honeycomb table comprising, in combination a table leaf 12having an outside surface 41, a pattern of mounting holes 13 in thattable leaf, a facing sheet 16 spaced from that table leaf, a honeycombcore 14 supporting that table leaf and extending inside that table leafbetween that apertured table leaf and that facing sheet 16 and havinginternal cells 38 between the table leaf and that facing sheet, andmeans for rendering that honeycomb table clean-room compatible,including sealing structure 25 extending continuously inside that tableleaf for sealing off the internal cells 38 against the mounting holes 13in the table leaf throughout said pattern. As can be seen from FIG. 1 ofthat Terry et al U.S. Pat. No. 4,621,006, the latter pattern includes atleast forty mounting holes sealed off by the sealing structure 25. Thesame applies to FIG. 1 of the subject patent application, which was FIG.1 of its above mentioned parent application Ser. No. 06/890,632, and tothe embodiments of FIGS. 9 to 14 of the subject patent application.

These and various other aspects, embodiments, modifications andvariations within the spirit and scope of the subject invention orequivalents thereof are apparent or will suggest themselves to thoseskilled in the art from the subject extensive disclosure.

We claim:
 1. In a method of manufacturing a honeycomb table including atable leaf having an outside surface and apertures for receivingfasteners for attaching objects at said outside surface and including ahoneycomb core supporting said table leaf and extending inside saidtable leaf between said table leaf and a facing sheet spaced from saidtable leaf and having internal cells, the improvement comprising incombination the steps of:providing a sealing sheet with projectionscorresponding in number and location at least to said apertures forprojection from said table leaf for a distance being smaller than aspacing between said facing sheet and said table leaf; and providingsaid sealing sheet between said table leaf and said honeycomb core forsealing said internal cells relative to said apertures, with saidprojections projecting away from said table leaf and said apertures insaid table leaf communicating with insides of said projections to rendersaid honeycomb table clean-room compatible by enabling cleaning of saidprojections inside said table leaf through said apertures from outsideof said table leaf.
 2. A method as claimed in claim 1, including thestep of:attaching said sealing sheet and said table leaf to each otherwith an adhesive applied to said sealing sheet and to an inside surfaceof said table leaf, opposite said outside.
 3. A method as claimed inclaim 2, including the step of:attaching said sealing sheet and saidhoneycomb core to each other with an adhesive applied to said sealingsheet and to said honeycomb core.
 4. A method as claimed in claim 1,including the step of:attaching said sealing sheet and said honeycombcore to each other at portions of said sealing sheet between saidprojections.
 5. A method as claimed in claim 1, including the stepof:attaching said sealing sheet and said table leaf to each other atportions of said sealing sheet between said projections.
 6. A method asclaimed in claim 1, including the step of:sealing said projectionsexcept for communication through said apertures.
 7. A method as claimedin claim 1, wherein:said projections are provided with closed sides andclosed bottoms relative to said honeycomb core.
 8. A method as claimedin claim 1, including the step of:using said sealing sheet as anintermediary in an attachment of said honeycomb core to said table leaf.9. A method as claimed in claim 1, including the steps of:providing asheet of sealing material; and providing said sealing sheet with saidprojections by drawing said projections in said sheet of sealingmaterial.
 10. A method as claimed in claim 1, including the stepof:providing said projections with a taper.
 11. A method as claimed inclaim 1, wherein:said projections project into said cells.
 12. A methodas claimed in claim 1, including the step of:providing damping masses onsaid sealing sheet in between said projections.
 13. A method as claimedin claim 1, including the steps of:composing said honeycomb core ofinterconnected first and second elements; and providing said firstelements between bottoms of said projections and said facing sheet, butproviding said second elements from said facing sheet to in between saidprojections.
 14. A method as claimed in claim 13, including the stepof:attaching end portions of said second elements to said sealing sheetin between said projections.
 15. A method as claimed in claim 13,including the step of:extending portions of said second elements pastsaid sealing sheet to said table leaf.
 16. A method as claimed in claim13, including the step of:extending said first elements below saidprojections back and forth between said second elements.
 17. In a methodof manufacturing a honeycomb table including a table leaf having anoutside surface and apertures for receiving fasteners for attachingobjects at said outside surface and including a honeycomb coresupporting said table leaf and extending inside said table leaf betweensaid table leaf and a facing sheet spaced from said table leaf andhaving internal cells, the improvement comprising in combination thesteps of:providing a load-bearing sealing structure with cavitiescorresponding i number and location at least to said apertures and witha height smaller than a spacing between said facing sheet and said tableleaf; and interposing said sealing structure between said table leaf andsaid honeycomb core so that said sealing structure bears the table leafand loads imposed on said table leaf, and so that said sealing structureseals said internal cells relative to said apertures and said aperturesin said table leaf communicate with said cavities in said sealingstructure to render said honeycomb table clean-room compatible byenabling cleaning of said cavities inside said table leaf through saidapertures from outside of said table leaf.
 18. A method as claimed inclaim 17, including the step of:attaching said sealing structure andsaid table leaf to each other with an adhesive applied to said sealingstructure and to an inside surface of said table leaf, opposite saidoutside.
 19. A method as claimed in claim 18, including the stepof:attaching said sealing structure and said honeycomb core to eachother with an adhesive applied to said sealing structure and to saidhoneycomb core.
 20. A method as claimed in claim 17, including the stepof:attaching said sealing structure and said honeycomb core to eachother at portions of said sealing structure located at said cavities.21. A method as claimed in claim 17, including the step of:attachingsaid sealing structure and said table leaf to each other at portions ofsaid sealing structure between said cavities.
 22. A method as claimed inclaim 17, including the step of:sealing said cavities except forcommunication through said apertures.
 23. A method as claimed in claim17, wherein:said cavities are provided with closed sides and closedbottoms relative to said honeycomb core.
 24. A method as claimed inclaim 17, including the step of:using said sealing structure as anintermediary in an attachment of said honeycomb core to said table leaf.25. A method as claimed in claim 17, including the steps of:providing asheet of sealing material; and molding said sealing structure andcavities from said sheet of sealing material.
 26. A method as claimed inclaim 17, including the step of:providing said cavities with arectangular cross-section.
 27. A method as claimed in claim 26,wherein:sides of said cavities are arranged in parallel to sides of thetable leaf.
 28. A method as claimed in claim 26, wherein:sides of saidcavities are arranged at angles to sides of the table leaf.
 29. A methodas claimed in claim 17, including the step of:providing said sealingstructure at the bottom of each cavity communicating with an aperture inthe table leaf with a break-out aligned with that aperture, to permit afastener extending through that aperture and that cavity to breakthrough said sealing structure without damage to the sealing structureand honeycomb core.
 30. A method as claimed in claim 29, including thestep of:reinforcing a periphery of said break-out with a hollowprojection.
 31. A method as claimed in claim 17, including the stepof:providing said sealing structure with projections extending intocells of said honeycomb core.
 32. A method as claimed in claim 17,including the steps of:providing said sealing structure with a bottomsheet; and rendering said sealing structure flexible by providing amultitude of slots extending between said cavities to said bottom sheet.33. A method as claimed in claim 17, including the steps of:providingsaid sealing structure with a bottom sheet; and providing a pattern ofcrossed slots having said cavities located therebetween.
 34. A method asclaimed in claim 17, including the steps of:providing said sealingstructure with a top sheet having upper portions of said cavitiesextending therethrough; and rendering said sealing structure flexible byproviding a multitude of slots extending between said cavities to saidtop sheet.
 35. A method as claimed in claim 17, including the stepsof:providing said sealing structure with a top sheet having upperportions of said cavities extending therethrough; and providing apattern of crossed slots having said cavities located therebetween andextending through a bottom region of said sealing structure.
 36. In amethod of manufacturing a honeycomb table including a table leaf havingan outside surface, and having a honeycomb core supporting said tableleaf and extending inside said table leaf between said table leaf and afacing sheet spaced from said table leaf, the improvement comprising incombination the steps of:providing apertures in said table leaf forreceiving fasteners therein for attaching objects at said outsidesurface; and rendering said honeycomb table cleanable through saidapertures.